Arrays and Pointers Arithmetic

Pointer Arithmetic

There are four arithmetic operators that can be used on pointers:

Pointers arithmetic is not same as normal arithmetic i.e. if you want to add 1 to any no. then you will get that no. after adding 1 in it. But in Pointers it is a bit different as: Base Address : The first byte address of any variable is known as base address. It means suppose you have int type variable then it's size in my architecture is 4 byte (It may vary in yours) then 4 consecutive blocks will be created in RAM. So when we will point it with any pointer variable at that time the address of 1 block of 4 will come in that pointer variable. It means base address is the first block address of any data type variable.

We can't add, multiply or divide two addresses. (Subtraction is possible)

                                

                                    // E.g:
                                    int a, b, *p, *q;
                                    
                                    &a*&b; // Not Possible
                                    
                                    &a+&b; // Not Possible
                                    
                                    p*q; // Not Possible

We can’t multiply & divide an address with integer value.

                                

                                    // E.g :

                                    &a*5; // Not Possible
                                   
                                    p/5; // Not Possible

We can add or subtract integer to/from an address.

                                
                                
                              // E.g :
                             
                              int a,b; // Let's Suppose &a is 1000
                             
                              int *p, *q;
                             
                              p=&a;
                             
                              q=&b;
                             
                              p+1; // It is possible [1000+1 = 1004]

Basically when we do
int a = 2;
a++; → 3

But in pointer
int *ptra = &a;
ptra = ptra + 1;
Now here it will add size of ptra (size of int)

Doing Arithmetic

                        

                                #include <stdio.h>
                                int main()
                                {
                                int a = 34;
                                int *ptra = &a;
                                printf("%d", ptra); // lets say this is x
                                printf("\n%d", ptra+1); // so this prints x+4, cuse that's the size of int
                                return 0;
                                } //we can use other operator too.

Output

3456780
3456784